Trunking system for telephone-exchanges.



F. R. McBERTY. TRUNKING SYSTEM FOR TELEPHONE EXCHANGES.

APPLICATION FILED SEPT. 8, 1309.

Patented May 11, 1915.

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FRANK a Iflc-BER-TY, or new ROCHELLE, new roan, essienon- To none rare CQMEAIW, on NEW YORK, n.1, a conronar onorjrnnncars.

rrnonnme systems i on Tnnnrnonn-nxcnanens.

To all whom itmay concern:

Bait known that I, FRANK McBnn'rY, citizen of the United States, residing at New Rochelle, in the county ofVVestchester and State of New York, have invented a certain new and useful Improvement in Trunk- 111 which the following is a full, clear, concise, andcxact description.

My invention relates to telephone exchange systems and particularlyto asystem of trunking in an automatic or semi-auto niatic exchange. Its obgect 1s in general to improve the condition ofthe connecting circuits with respect to their use in transmitting telephonic currents.

Other objects are to control the operation of signals and to bring about disconnection of telephone lines connected over circuits including a trunk line, and'to accomplish these results without, flow of current inthe trunk line, and preferably also without a connection from any part thereof to ground or to other circuits during the period of use of the lines for telephonic communication. The freedom from (low of current in the trunk line is advantageous because, among other reasons the presence of current through the various contacts of selectors or other switch mechanisms is liable to cause noise in the telephone circuits. The absence of ground or other connections to the trunk circuit makes it-more easily balanced with respect to induced currents from other circuits.

Someof the features of a semi-automatic telephone exchange system to which my invention has been appliedmay be described briefly as follows: The telephone lines of various subscribers stations extend some to one and some to another or other distant central oiiices and there terminate in suitable connecting switches such as spring ack switches at A boards and automatic switches or selectors at B boards. At each office, connecting'circuits are provided at the A boards and these may have-plugs adapted to be in sorted in the spring jacks. These connecting circuits lead to the brushes of selectors, the fixed terminals of which are connected through interofiice trunk lines to the brushes of other selectors at'the B boards of the dis tant offices. The terminals of the last incntioned selectors may lead either directly to the telephone lines, or, as in large systems,

Specif cation of Letters Eatcnt.

application filed September 8, 1909. Serial No. 516363.-

Systems for Telephone-Exchanges, of

Patented through ofiice-trunk lines and other selectors and thence to the telephone lines It will be suflicient, for the purpose of describing my invention, to consider a single such inter ofiice trunk line and two telephone lines adapted to be connected therethrough for telephonic communication, togetherwith the apparatus and circuits involved in'signaling over the trunk lines and in the control of the disconnection of the lines at the termination of the conversation. 1

It is desirable, on account of the cost of line wires, that each interoiiice; trunk line comprise but two wires between the oflces, these wires serving the purposes of telephonic transmission between the connected telephone lines, of-signaling and of controlling the connecting switches or selectors.

it is also desirable, and it is customary in such trunking systems, to supply current to the connected telephone lines by two batteries, one at the A board for the-calling line,

the trunk circuit serve the purpose of permitting the telephonic currents to be trans V mitted from one subscribers line to the trunk circuit,'and from the trunk circuit to the other line while conductively separating the line and trunk circuits from each other,

In such a semi-automatic telephonoicfchange system as the one being considered, anoperator-is stationed at the A board. Her-duties are (,1) to make connection with the calling line by inserting the connecting plug; in thevline springjack when the 'sub-' scriber cal-ls; (2) to set upon snitable controlling or sending mechanism a condition adapted to cause. the automatic switch-to pick out and. make connectionwith the line of the desired called'subsci'iber; and when the conversation is "completed and the subscribers have hungup their telephones, thereby causing signals to be operated at the A board, to withdraw the plug from the springjack, or to perform some other manuals act, thereby causing the selectors to be re switch shall be wholly under the control of mechanism made operative from the distant end of the trunk line.-

According to my invention the changes in the trunk line for purposes of signaling prevented from eifecting the restoration of the automatic switch by means of the fol-,

lowing arrangement. The trunk line is closed at both ends; it is provided at the end nearest the automatic switch with switching mechanism adapted to inter-pose a source of current therein; a device is included in the trunk line responsive to current from said source and adapted to control the re storing mechanism, and means operated in the movement of the switching mechanism is'provided to reverse the control of said de vice over the restoring mechanism. The restoring mechanism is preferably controlled by a magnet and the device in the trunk line for the control thereof is preferably a relay which controlsthe restoration of the automatic switch by means of a circuit for the restorin' ma net. This circuit man be one having two paths adapted to be closed in alternate positions respectively of the arms ture of the relay and the switching mechanism referred to may have an element adapted in the movement thereof to change the connection of the circuit from one of said paths to the other. The switching mechanism may be controlled by a relay in the calledtelephone line which relay is in turn controlled from the substation of the line, in which case the continuity of each of the two paths of the circuit for the restoring magnet is controlled by the relay.in the trunk line and by the relay in the telephone line. The device or relay in the trunk line which controls the restoring magnet of the automatic switch may be made operative to effect the restoration of the automatic switch by means of a source of current interposed in the trunk line at the other end thereof by suitable switching mechanism. This last mentioned switching mechanism is preferably arranged to be operated in successive stages to open the trunk line and to interpose therein the last mentioned. source of current. The opening of the trunk line operates the controlling device for the restoring' mechanism when the first mentioned automatic source of current is included in the trunk line and the closing of the trunk line through the last mentioned source of current causes the response of the controlling device for the restoring magnet when the trunk line is closed without the interposition of the first v telephone line is preferably so arranged that upon the opening of the telephone line at the substation switch it operates the switching mechanism referred to to 1nterpose a source of current in the trunk line to cause the response of the signal at the distant end of the trunk line.

The accompanying drawing shows diagrammatically that part of the apparatus and circuits of-a semi-automatic telephone system which embodies my invention.

In the drawing, 1 and 2 represent calling and called telephone substations, respectively, and 3 and 4 the switches thereof, substation 1 being connected by line wires 5, 6,

"to a springjack 7 at a switchboard A, and substation 2 bein connected by line wires 8, 9, to a pair of Xed terminals 10, .11, of a selector 12 at a switchboard B. A plug 13 of a connecting circuit 1-1 is shown as in.- serted inthe springjack, this connecting circuit including windings 15, 16, of a repeating coil 17, the opposing windings 18, 19, of which lead to a pair of brushes 20, 21 of a selector 22; The circuit from the selector is extended by way of a pair of fixed terminals 2-8, 24,- thereof over trunk line conductors 25,26,to the windings 27, 28 of a repeating coil 29, the opposing windings 30, 31 of which leadto a pair of brushes 32, 33 of the selector 12;

Between windings 15 and 16 is a -bat tery 34 which supplies current over the calling line 5, 6, to station 1. Windings 18 and 19 are adapted to be connected either through a conductor 35 without the interposition of a source of current or through conductor 36 including a battery 37. The connection through one or the other of these conductors is controlled by a sequence switcl 38, which will be described presently.

A local circuit 39 including the winding of a relay 10 is controlled hrough the sleeve contacts of the plug 13 and spring-jack 7 so that the relay is energized when the plug is inserted. This relay controls a local circuit 41 which becomes closed when relay 10 is deenergized. lncluded in the circuit of intents the trunk line at the A board is a relay- 42 controlling in a local circuit a supervisory lamp signal 4-3, the lamp being lighted when the relay is energized. interposed serially between windings 27 and'QS of the repeating coil 29 is the winding of a relay l4 and a conductor 45 controlled by front contacts 46, 47 of a relay t8, the circuit being thus closed without the interposition of a source of current when relay 48 is energized An alternate path between said windings includes a conductor 19 and a battery 50 this path being closed through back contacts 51,- 52 when relay 48 is not energized. i

The circuit of the called line when con-' 'nected at selector 12 as shown in the draw? ing, includes battery 50 which is interposed between windings 30 and 31 of the repeating coil 29. A relay controllin the local circuit of relayfl8 is included in the circuit and responds to the operation of switch 1- at station Relays 44- and 48 jointly control a local circuit 51 which may be closed through either of two paths, 55, 56 path being operative through back contacts 57, 58 when the relays are deenergized and 56 through front contacts 59, 60 when the relays are energized. This local circuit controls the operation of a sequence switch 61 which will be described presently. A condenser 110 is preferably bridged about the winding of relay -14- and the forward contact -16 of relay 18.

. Selectors 12 and 22 may have their fixed terminals arranged in curvedrows upon a cylindrical frame, as indicated in the drawin'g, the r0ws of terminals being adapted to be traversed by the brushes which are rotatably mounted upon spindles 62. The brushes of the selectors are arranged to be rotated by power magnets 63,;therevolving pole pieces'het of which attract power plates 65 flexibly mounted upon spindles 62 when the magnets are energized.

The sequence switches 38 and 61 may be iif'the same general construction and mode of operation. Only so much of each of them is shown as is helpful in describing the op eration of the structure of this invention. Referring to sequence switch 38, 6G to 69 in- :clusive are cam wheels, preferably of insu hating material, mounted on a shaft 70. Each cam wheel engages spring operating switch contacts. At the lower end of the shaft is a circular pole-piece 71 and a power magnet 72, the pole-piece being adapted to be engaged by a rotating armature 73, which is mounted on a'continuousjy rotatin shaft 74 by suitable motor mechanism. ontact springs 7 5 and 76 controlled by cam wheels 00 and 07, respectively, normally rest against contact pieces 77 and 78 forming the terminals of conductor These wo cam wheels have raised portions 79, 80 which are adepted, upon the first stage of movement in the the calling substation 1.

rotation of the shaft to move the contact springs into midway position with respect to the opposing contact pieces. The raised portions 81, 82 are adapted upon the second stage to move the springs into contact with contact pieces 83 and 84, which form the terminals'of conductor 36'. can; wheel 68 is adapted, when theishaft is rotated after a brief period, to move its contact spring 85 into connection with contact piece 86, con- .nected to' ground, while cam wheel 69 is- :engage contact piece 93, connected to ground,

and cam wheel 91 is adapted in the same manner as is cam wheel 69 of sequence switch 38, to cause contact spring 95 to maintain connection with contact piece 90 until the raised portion 97 engages the spring. Pole piece 98, magnet 99, rotating armature 100 and shaft 101 correspond to like parts of the sequence switch 33.. In either switch the energizatien of the power magnet causes the rotating armature to en: gage the pole piece fixed to the shaft and causes the rotation of the cams. Power magnet 72 is controlled by local circuit 11, which includes contacts 87, 88 and a battery 102. Similarly power magnet 99 is con-. trolled by local circuit 54: whichincludes contacts 95, 96 and a. battery 103. These power magnets may be operated through other circuits than those shown, and I have indicated by branch wires 109 that such other circuits may be provided as required in the system. Power magnets 63 of the selectors are controlled by local circuits 104 and 105 including contacts 85, 80 and 02, 93 and batteries 106 and 107 respectively.

The apparatus and circuits are shown in condition for telephonic communication between the substations of two lines, because the operation of the structure so far as this invention is concerne involves principally this condition of the lines and trunk cir cult and their disconnection after use by the subscribers. During this period of telephonic communication the talking circuits may be traced as follows: Battery 34' supplies current by way of windings 15 and 16 of repeating coil 17 through contacts of the plug 13 and jack 7- and line wires 5, 6 to switch 3 and the telephone instruments at Battery 50 likewise supplies current by way of windings 30, 31 through brushes 32, 33, terminals 10, 11 of selector 12 and line wires 8, 9, to switch 41 and the telephone instruments 'at the called substation 2. The intermediate or trunk circuit by which the two telephone ioo iio

i'is

irio

&

lines are inductively united is, during this period a closed circuit which includes no source .of current and which is entirely free from connection with ground or other circuits. It includes at the A board windings 18, 19, of repeating coil 17, relay 42, contacts 75, 77 and 76, 78 conductor 35 and brushes 20, 21 and terminals 28, 24 of selector 22; and at the B board, windings 27, 28 of repeating coil 29, relay 44, contacts 46 and 47 of relay 48and conductor 45, the

circuit being completed by the trunk line wires 25 and 26, which may extend for a considerable distance between the two boards To enable these talking circuits to be more readily traced the conductors thereof are shown in heavy lines.

When the subscriber at the called station 2 replaces his telephone on its switch hook,

. the A board and the lighting of the supervisory lamp 43, thus giving the operator a signal that the called subscriber has completed his conversation over the circuit. Relay 48 also opens contact 60 and closes contact 58. Relay 44, however, at the same time receives current from battery 50 and opens contact 57 and closes contact 59. The local circuit 54 of power magnet 99 of the se quence switch 61, therefore, remains open- In response to the supervisory signal, the operator withdraws plug 13 from springjack 7, causing the opening of local vcircuit 39 of relay 40, which in turn closes the local circuit 41 of power magnet 72 of sequence switch 38. The cam wheels begin to revolve in the direction ,of the arrow and change circuits as follows First, the circuit of the trunk line is opened by reason of the raised portions 79 and .80 of cam wheels 66 and 67 lifting springs 75 and 76 from their normal resting contacts 77 and-78, respectively. Second, relay 44 is deenergized and,

its armature in falling against its back contact 57, closes circuit 54 by Way of conductor 55 and back contact 58 of relay 48 to the power magnet 99 of sequence switch 61.

Third, power magnet 63 of selector switch 12 is energized over its circuit 105 including contacts 92, 93 and battery 107. The brushes 32, 33 are therefore moved away from the terminals 10, 11 on which they .were resting and the circuit of the called line is disconnected. Fourth, the continued movement of sequence switch 38 brings the raised portions 81, 82 of cam wheels 66, ,67

under springs 7 5 and 76 respectively. and

closes the trunk circuit again through conductor 36 which includes battery 37. This looping in of battery 37 performs no func tion under the present assumed condition that the called subscriberhad placed his telephone on its switch hook. Fifth, after a brief interval springs and 76 resume their normal position as shown in the drawingand spring 85 is lifted by the raised portion 108 of cam wheel 68, thus closing the circu'it'of power magnet 63 of selector '22, which moves the brushes 20, 21 away the power magnets 63- may be openedat contacts 85, 86 and 92, 93 respectively.

The operator may disconnect the lines be fore the called subscriber has hung up his telephone, and the operation in that case is as follows: The plug is removed from the springjack at the A board, and the circuit of power magnet 72 of sequenceswitch 38 is closed at relay 40 in the manner before described. The opening of the trunk circuit at contact springs 75 and 76 has no effect on the operation of the apparatus at the B board. The continued 'movement of sequence switch 38, however, loops battery 37 in the trunk circuit and causes a flow of current which energizes relay 44. This relay in turn closes local circuit 54 to power magnet 99 by way of conductor 56 and contact 60 of relay48. The sequence switch 61 closes the circuit of power magnet 63 of selector'12 asbefore described. It will thus be seen that in either condition of the apparatus at the 13 board, that is, either while thetelephone is off the switch hook at the called subscribers station, or while it is on the hook, the operator at the A board may bring about disconnection of the lines simply by the removal of the plug from the springjack of the calling line. The circuit of the trunk line between the and B boards will either be with or without a source of current at the B board, and the sequence switch by successive changes in the condition of the circuit at the A board I neciec.

" sequeuce swif-ficlies migl'l; be employed board to change the circuit of' the liue successively to meet the two coni like B board. the sequence .i board. might be omitted and )pci'ation of disconnection cont-rolled.

more directly apparatus intlieahiunk line.

li es ifci'uis clevices for inductively conneczing W ile conduc' vely separating the trunk line a the selephone lines may be subsiitutccl. for the repeating coils if desired. Some other device films uv plug, and jack may be employed es the means of connecting the calling line in circuit and the control of the apparatus to cause disconnection may be lied by some other set than the removal sf :1 plug from the spcingjuckj Although I new shown several batteries for the sake oi clenini s in illusti'zicing circui bs, 1 is be understood that one batteyy each ure. may be employed would ...y be plreierred in. the place of show e mi n v :in'ei not i nited to in oi rsilus cu'cuiis'wlncli l1 clcsci'ib out is defined the follin. l\l

. claims:

im. I

a zeleplione exchange sjzs'liem, the iliion with. en cucomatic swifiching uppui'ufius s ii'uuk line consisting of 2L pair of comluccoi's mlupled to fOl'l'l'l part of the talking CllClllL, 2m substation lines 0011-- through said. eutoiiietic switching apparatus and trio. line, of means operable upon she opening of She subsfiution line of the called subscriber for including a source of current in. iJilQ trunk line and an obi-o- "pensive oil-c1 i-conti olling device mil; by curious from said source.

in .v telephone QI-ICl'lflllg'Q system, the i-lOll with cinematic switching sue-us, :1 trunk ine consisting of conductors ails to form part of e cuicuit, 11ml subsiciion lines couthrough seiiil autii nmtic switching so itirunk line, of :1 switch ii} the 'iJlOl'l of the called. subscriber adapted the line when in. use, means at one said ii line open upon the eplione exchange Z1 1 somatic p missius bruni: line consisting oi.

ecoclucl ilidsufieni to form poi": 'l' and subsc connection ithrough suio. an

e trunk line, en'cl e responsive source of currentin th signaling devicein the i'unlit line u said source of'cui-ienlz.

4 is a telephone exchange system, the combination with en. euiioiuecic switching apparatus, trunk line consisting of e of conductors seiepieil ifio form part of tile ialking circuit and. substation linespliysi Cally disconnected from but inductively connected to said trunk line, automatic switching apparatus uniting said substation line to said inductive connection, of a plug and jsck switch included in the circuit of one of said substation lines; means operable upon the removal of the plug for including a1 source of current in the cruel; Que, and an electroresponsive circuiucouti'ol lg device actuated. by current from said. sou

5. In a celeplione exchange fills I combina fiion with en eusomcfiic switching apparatus a, trunk-line consisting of e pair of conductors mispeel form part of the talking circuit and substation lines cossecs-cc? through automatic switching apparatus and i i uni; line, of connecting switch inclmiecl in too circuii; of one of ssiii. substation lines, nieens one curl of sold firuuk line operable upon the opening 05 saici switch adepileel in successive stages to open said irunlc line encl to interpos d-therein a source of current, end a circuit controlling device as the other-cool of sa is. truck line responsive toseicl' source of current.

'6. In a telephone exchange system, the combination with eufiomctic switcli t apparatus, a. closccl trunk line. consisting of 2, pair of conducors adapted to form part of the talking circuit and. :lSIZbSfifiLlOD.

physically clisconuecizeii i'oiu lout 1. i

1 connected to ssiii 'Euunlc line, P switching apparatus unitingseid subsini .0 line 20 seiol inductive connection, of iiig iuecl'icuisin for euiomutic apparatus and adeptedic incluoe 2 source of current lie trunk line so effect l lo the operation of saici restoring Lueciieuisicw 7. In a telephone exchange system, combination with an eutomusic switching apparatus a closef. fiiuui: line consisting of a pair of conductors uelapieil of the calling circuit and s l physically disconnected 1 connected to suicl trunk line, station lines being connected ing zuechenisln. of restoring seicl automatic. sw 'zcliii means operable when the cum; of

of said substali-ioo lines is open in nc.

ource of current i said automatic switching apparatus, of .a signal device in the trunk line and means operable upon the opening of said substation line for including a source of current in the trunk lineto effect the operation of said signal device.

9. In a telephone exchange system, the combination with an automatic switching apparatus, a trunk line and substation lines connected through said automatic switching apparatus and trunk line, of restoring mechanism for said automatic switching apparatus, means operable whcnthe circuit of one of the substation lines is open for in- J eluding a source-of current in the trunk line to effect the operation of said restoring mechanism, a signal device in the trunk line and means operable upon the opening of the other of said substation lines for including a source of current in the trunk line to effect the operation of said signal device.

a 10. In a telephone exchange system, the combination with an automatic switching apparatus,- restoring mechanism therefor, a trunk line and substation lines connected through said switching apparatus andtrunk line, of means operable when the circuit of one of said substation lines is open for ineluding a source of current in the trunlc line to effect the operation of said restoring mechanism, means operable upon the opening of the other of said substation lines for including a source of current in the trunk line and means for preventing the last'mentioned source of current from effecting the operation of said restoring mechanism.

11. In a telephone exchange system, the

combination with an automatic switch and 40 line, a source of current, switching mechanism adapted to. interpose said source of current in the trunk line, controlling means for said restoring mechanism responsive to changing said controlling means to reverse the mode of control thereof over said restoring mechanism.

12. In a telepho'neexchange system, the

combination with an automatic switch and restoring mechanism therefor, of a trunk.

line closed at one end, a source current at the other end thereof, switching mechanism adapted to interpose said source or for said restoring mechanism responsive to l current in the trunk line, and means opercl osed in alternate restoring mechanism therefor, of a trunk current in the trunk line, and means for current in the trunk line, controlling means closed atone end, a source of current at the nices /s by said relay,- and means operated in the movement. of said switching mechanism adapted to change said circuit to-i'everse the mode of control of said relay over said restoring magnet.

- 14. in a telephone exchange system, the

combination witnanautomaticswitch and a restoring magnet therefor, of a trunk line, a source of current, switching mechanism adapted to interpose said source of current in the trunk line, a re ay included in the-- trunk line and responsive to said sourceof current, and a circuit for said restoring magnet having two paths adapted to be positions, respectively, of the armature of said relay, said switching mechanism having an element adapted in the movement thereof to change the connection of said circuit from one of said paths to the other.

15. In a telephone exchange system, the combination with an automatic switch and a restoring magnet therefor, of a trunk line, a source of current, a telephone line and a re lay included therein controlled from the substation thereof, switching mechanism operated under the control of said relay and adapted to interpose said source of current in the trunk line, a relay in the trunk line responsive to said source of current, a circult for said restoring magnet having two paths, the continuity of each of which is controlled by both of said relays.

16. in. a telephone exchange system, the

combination with an automatic switch andrestoring mechanism therefor, of a trunk line, a source of current, switching-mechanism adapted to intcrpose said source of current in the trunk line, controlling means for said restoring mechanism responsive to current in the trunk line, means for changing said controlling means to reverse the mode of contrhl thereof over said restoring mechanism and a signal device in the trunk line responsive to said source of current. 17. in a telephone exchange system, the combinationvwith an automatic switch and restoring magnet therefor, or" a trunk line closed at both ends, and having atone end a source of current, a telephone line, a'relay responsive'to current in said telephone line, switching inechanism-undertlre control of said relay and adapted to interpose said source of current in the trunk line, a. relay included in the trunk line and responsive to said source of current,'a signal device in the trunlc'line at the other end thereof, and'a circuit. for said restoring magnet having two paths the continuity of each of which is controlled by both of said relays.

the other end oi W messes s telephone exchange system, the comb; 1510?" with an automatic switch smi i'estoi rig mechanism therefor e li-ilii lk lice consisting of 2 pair of conductors soap.

sou cc of co rent, switching iceclie-Jiism scleptecl to inteipose said source of current in series in the trunk line and clevice in the time line responsive to ssiol source of current and eclepted to 'efiecttiic'opemtios of said i'estoring mechanism.

is. In a telephone exclisoge system the combination with so automatic switch and restoayiiig mechaiiism tlierci'or, of a trunk line closecl at both ends, is source oi current at one end, switcnmg mechanism to 111te1oose sew-source of s'illii'fiiil) mthe,

combination of a trunk line closest cctli mechanism adapted. to control the circuit of said trunk hue and a local circuit for said EL'QS JOZlII ms "net controlled ointl I C: J u

said relay and. an element of said last men.-

switcliing mechanism.

21. in telephone exchange system, the combination with en. automatic switch and restoi-in mechanism therefor o1 EL trunk line cores of current one; switching mesh eoism adapted to ii terpose ssfl source cui'rent in the trunk line at one end thereof control i means fob said restoring mechm nisin resgion We to current in the trunk line means operating in the movement or said switching mechanism adapted to change ss'icl controlling means to reverse the Il'lOiliQ of control thereof over said restoring mechanism, and a source of current and switching mechanism st time other end of saicl trunk the 12st m-entioiierl sWi ii" 'msclisacted in successive stages to *i 1- UQIIltJQRQ'i so eplione iof current system, the emetic s .tch of it fiillilk line o e end thereof, switclb to interpose said t in he trunk and a recc "e o isive to said 1e, role-y icrein, circle for two paths the oh contlolle-fi by ccmbinetioii a XQSE 1:12a :1 solo-cc i meciisnism somce OI cum-e in the t uni; S01 ceoi cum respcoisive to cur ssio". IFQSeOX'lHg msget ccntimzity of each. oi both of said relays, s, so

=.e and to interpose these automatic switch a phone line coiiti'olleci the opening; of tliesuosta mes-schism etle1te in saceessive stsges to open the tmi klline smite intergiose the' lest meotione. source of cmt ere 23., 13c telephone exchange syslem, the combiiictior mecssnism i16I3f "f a trust: lies, a source of current at one end thereof,

switciiing mechanism adeptezi to iii'wsposei sefi source'of. current in the tmmk line,

cost-Polling mesiis for said; restoringmeclm;

switching messmsm, sci i signal lGVlCB be 'ing iscluciecl in the trunk line responsive, to the first mentioseol source of current, and

the mentiooeci' switoiiing mechanism -be w th so sutomstic switch sci;

d vice and iiig esptetl in successiige stages to open said trunk line to im'erpcss thereiii last mentioned source of correct. 24:. In telephone exciisiiige system ends, said. trunk line having at one coil so automatic switch controlling the continuity of the circuit of 2; called telephone line, i e storing znechaiiism for seicl switoli, and s controlling device in the trunk line for said restoring mechanism, said trunk line having the other end msnosl switch controlling the continuity of the circuit of e caliing tele-i phone line, an automatic switch controlling the continuity of the circuit of seiai truck line, restoring mechanism for icl automatic switch, a source of ocqiswitcliim'g mechanism, said switching mechanism bein under the control of said manual switch ens adapted to interpose source of current in the trunk line to cause the societies of the controlling device it; the trunk line and said switching mechanism having an element controlling the operation of the restoring mechanism of the last mentione automatic switch.

2?. In a. telephone exchange system the combination with an switch, is storing meci'isn'sm therefor, 11 eie phooe line the circuit of which controllcfi by seiol telephone line closing the circuit of the talecy flow of therein, of trunk l s source of current at one em}. thereof, switchiiig mechanism conti'olled'by said device eml ailtd upon rsiige to close saiol its use and a device 1.

terpose seiol solirce of current line, a sigosldevice thetrm. 1.718 at the other cool thereof i'es ponsive (l source aren't, cost-rolling means o? ssicl recg mechanism zesoossiw current in siicststioil switch atcurrent Elli iii-ac ogaexetisggi Lathe.

- controlled by a flow of current therein, of a Y 26. In atelephone exchange system, the

combination with an automatic switch, re-

storing mechanism therefor, a telephone line,

the circuit of which is controlled by said automatic switch, a substation switch ar ranged to close the telephone line during its use and a device in the circuit of the line trunk line, a source of current at one end thereof, switching mechanism under the con- .trol of said device adapted to include said source of current in the trunk line'when the substation switch is open, controlling means for said restoring mechanism responsive to "current in the trunk line, means operating in the actuation of said switching mechanism adapted to change said controlling means to reverse the mode of control thereof over said restoring mechanism, a source of current at the other end of the trunk line and switching mechanism adapted in suc 'ssive stages to open the trunk line and to close it through the last mentioned source of current.

27. In a telephone exchange system, a pair of substation lines, a talking connection established from one of said lines to the other, an automatic switch through which the, com e'ction' extends, a closed trunk line forming part of said connection physically disconnected from'but inductively connected to saidlsubstation lines, a restoring mechaanism for 'saiidrautomatic switch and means for including a source of current in said closed trunk to effect the operation of said restoring mechanism.

28. In a telephone exchange system, automatic switching apparatus, a closed trunk line and a subscribers line connected to said trunk line by said automatic switching apparatus, a second substation line physically disconnected from but inductively connected to said trunk line, restoring mechanism for said automatic switching apparatus, and means actuated upon opening the said sec ond substation line for including a source of current in the trunk line to effect the operation of said restoring mechanism.

29. In a telephone exchange system, automatic switching apparatus, a closed trunk line and a substation line connected to said trunk line by said automatic switching apparatus, a second substation line physically disconnected from but inductively connected to said trunk line, restoring mechanism for 7 said automatic switching apparatus, means actuated upon opening either substation line for including a source of current in the trunk line, and electromagnetic devices, one at each end of said trunk respectively responsive to the inclusion of current in said trunk at the opposite end thereof.

Inwitness whereof, I hereunto subscribe my name this seventh day of September A. 1),, 1909.

FRANK R. MGBERTY.

\Vitnesses I IRVING MAoDoNALD, EDGAR F. BEAUBIEN. 

